The vitrification of highly radioactive waste solutions is carried out in a ceramic melting furnace. It is necessary to take samples from the melting furnace in order to be able to carry out the vitrification process and in order to be able to determine density-related deposits in the molten glass such as metals and rare metals. Previously, glass residues at the base drain of the melting furnace were taken as samples. In this situation, the taking of samples is confined to the area of the outlet orifice. Any deposits which may occur in some other area of the glass melting furnace cannot be examined.
German Pat. No. 2,911,008 discloses a device for taking molten glass from a bath or from a glass melting furnace. The device comprises a rod rotatable about its axis and adapted for insertion into a tap hole provided in the side wall of the glass melting furnace. The rod is rotatable and can be dipped into the molten glass with its free front end. This rod can be removed substantially axially from the side tap hole.
The metals are rinsed off in the molten charge as the device is withdrawn because of the varying density of the molten glass and the heavy and rare metals. Accordingly, it is impossible to obtain a representative sample with this device.